The present inventions relates to an acoustic system and method in a well. More specifically, the present invention relates to an acoustic system and method for acoustic communication over an acoustic medium comprising production tubing, well casing or over continuous tubing in a well (e.g., coil tubing, chemical injection tubing or dewatering string).
After an oil or gas well has been drilled it is completed. A completed hole includes a casing defining the hole with production tubing installed within the hole. Oil or other petroleum products are extracted via the production tubing, as is well known. Typically, the production tubing includes sensors and electromechanical devices located downhole for control of the production well. The sensors monitor downhole parameters (such as pressure, temperature, flow, gas influx, etc.). Examples of electromechanical devices include, e.g., a sliding sleeve or packer, a valve or start/stop a pump or other fluid flow device.
Communications uphole/downhole with the sensors and the electromechanical devices is generally accomplished over a wireline, as is well known in the industry. Another way of communicating is described in U.S. Pat. No. 5,283,768 (""768) assigned to the assignee hereof. The ""768 patent discusses acoustic telemetry in the completion liquid in the annular space between the casing and the production tubing in a production well, i.e, the completion liquid is the acoustic transmission medium. The acoustic transducer disclosed in the ""768 patent generates acoustic waves in the liquid.
The above-discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by the acoustic transmission system of the present invention. In accordance with the present invention, acoustic communication is transmitted over production tubing (the production tubing is the acoustic transmission medium) or over coil tubing in the production tubing. Preferably, a broad band communications technique is employed to ensure that any transmission is properly received.
A production well (i.e., completed well) is enclosed by a casing with a rig at the surface and has production tubing installed therein. The lower end of production tubing is perforated to provide a path for the flow of oil from the hydrocarbon bed up the center of the production tubing. A packer is provided to isolate this lower end from the upper portion of the well. Sensors are provided to monitor downhole parameters (such as pressure, temperature, flow, gas influx, etc.) and electromechanical devices include, e.g., a sliding sleeve or packer, a valve or pump or other fluid flow devices for control. Such sensors and/or electromechanical devices may be mounted downhole in the production well itself and/or incorporated into the production tubing, as are well known. A downhole acoustic communication tool in accordance with the present invention is permanently deployed downhole and is provided for acoustic telemetry. An uphole acoustic communication tool is provided for acoustically communicating with the downhole tool.
The downhole acoustic tool in accordance with a first embodiment, comprises a cylindrical mandrel having rotary connections the ends thereof. This tool, when installed in a production well, becomes part of the production tubing. An opening extends longitudinally through the mandrel permitting flow of oil or gas therethrough. The mandrel includes a plurality of machined cavities wherein the components of the tool are housed. A piezoelectric ceramic transducer (i.e., a stack of piezoelectric elements) is mounted in one of the cavities in a compressed state and in intimate contact with the mandrel for acoustic coupling therewith. Transformer coils, an electronic assembly and a battery pack assembly are mounted in another cavity. A sleeve is connected onto the mandrel by a rotary connection. The sleeve covers the cavities in the mandrel. A locking ring attached at another rotary connection and a shoulder sub are provided to secure the sleeve on the mandrel. The mandrel, if disposed downhole in a production string without the sleeve would subject the mandrel to high stresses, whereby the piezoelectric stack therein would be unloaded or over loaded resulting in poor acoustic coupling. The sleeve, by way of the rotary connections, absorbs much of these stress, whereby proper loading on the stack is maintained.
In accordance with a second embodiment, a coil tubing is extended down the opening of the production tubing. An uphole acoustic tool (e.g., an acoustic receiver, for example, an accelerometer) and a downhole acoustic tool (e.g., an acoustic transmitter, for example a piezoelectric device) are provided on coil tubing for acoustic telemetry in accordance with this alternate embodiment. It will be appreciated that two-way acoustic communication is within the scope of the present invention, e.g., piezoelectric transceivers uphole and downhole. It will further be appreciated that coil tubing is also employed while drilling a borehole, and acoustic telemetry as described herein may be applied such coil tubing. Also, the acoustic telemetry of the present invention, as applied to coil tubing, may be applied to other continuous tubing strings, e.g., chemical injection tubing, a dewatering string and the like. The downhole sensors are connected to the downhole acoustic tool for acoustic communication.
In accordance with a third embodiment, a downhole acoustic communication tool is provided for acoustic telemetry which is integral to casing. An uphole acoustic communication tool is provided for acoustically communicating over with the downhole tool.
The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.